The proposed project extends our ongoing longitudinal study of substance use among children of alcoholics (COAs) into young adulthood. The overall goal continues to be determining the extent of COA risk for substance use and abuse and identifying mediating mechanisms underlying this risk. These mechanisms are of theoretical importance for understanding the etiology of substance abuse, and practical importance for designing preventive interventions. Young adulthood is of particular interest because of its high rates of substance use and abuse. Accordingly, we aim to examine the effects of parent alcoholism on young adult substance use and abuse outcomes, and on trajectories of use from adolescence to young adulthood. We examine the psychosocial mechanisms underlying these effects and the consequences of parent alcoholism and adolescent substance use for the important developmental transition to young adulthood. To achieve these aims, we propose a follow-up of our COA and control subjects who will be 18-25 years old, their parents, and peer informants. We also propose to include 400 full biological siblings of our subjects who will also be 18-25. The sample is drawn from the community rather than treatment settings, and includes alcoholic mothers and fathers, and both "active" and "remitted" alcoholics. Parent alcoholism and associated psychopathology were directly ascertained rather than relying on offspring report. Beginning when subjects averaged 12.7 years of age, they and their parents received 3 annual computer-assisted interviews. These multiple reporter data were (and will be) used to minimize the impact of response biases. At follow-up, computer-assisted interviews will be conducted with the young adults, their siblings, and their parents, and telephone interviews will be conducted with peer informants. Young adult outcomes to be assessed include substance use/abuse, other psychopathology, positive outcomes, and the resolution of age-appropriate developmental tasks. Hypothesized mediating variables are derived from theories of substance use and abuse including parent/peer socialization models, stress and negative affect regulation models, temperament models, and models emphasizing cognitions about substance use. Data analytic strategies include hierarchical linear modeling to assess the impact of parent alcoholism and family climate variables on young adult substance use and abuse outcomes, and longitudinal latent growth curve modeling to assess the impact of parent alcoholism and psychosocial risk factors on growth curves of substance use from adolescence to young adulthood. The findings will be of particular relevance for prevention because they focus on a high-risk group, and track the natural history of substance use from its precursors to the development of clinically important end points.